Horton

Re: Parallel bitmap heap scan

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Rafia Sabih <rafia.sabih@enterprisedb.com>
Cc: tushar <tushar.ahuja@enterprisedb.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-01-13T13:06:16Z
Lists: pgsql-hackers

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On Thu, Jan 12, 2017 at 5:47 PM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
>> Hello Dilip,
>> I was trying to test the performance of all the parallel query related
>> patches on TPC-H queries, I found that when parallel hash [1 ]and your
>> patch are applied then Q10 and Q14 were hanged, however, without any
>> one of these patches, these queries are running fine. Following is the
>> stack trace,
>
> Thanks for reporting, I will look into this.
I had setup for TPCH scale factor 5, I could reproduce the hang
reported by you with Q10. I have fixed the issue in v10 (only 0003 is
changed other patches have no change). However, after fixing this
issue it's crashing in parallel shared hash patch and call stack is
same what you have reported on parallel shared hash thread[1]

[1] https://www.postgresql.org/message-id/CAOGQiiOJji9GbLwfT0vBuixdkgAsxzZjTpPxsO6BiTLD--SzYg%40mail.gmail.com

Please verify with the new patch.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Pass DSA_ALLOC_HUGE when allocating a shared TIDBitmap.

  2. Support parallel bitmap heap scans.

  3. tidbitmap: Support shared iteration.

  4. Shut down Gather's children before shutting down Gather itself.

  5. Revise the way the element allocator for a simplehash is specified.

  6. Refactor bitmap heap scan estimation of heap pages fetched.

  7. Use more efficient hashtable for tidbitmap.c to speed up bitmap scans.